Australia's iconic Great Barrier Reef is experiencing an unprecedented mass coral bleaching for the second consecutive year, scientists said today, adding that the corals do not have enough time to fully recover from last year's extreme heat event. The bleaching is part of a global event affecting the world's coral reefs over the past two years. Experts from the Great Barrier Reef Marine Park Authority spent six hours yesterday flying over the Reef between Townsville and Cairns, alongside researchers from the Australian Institute of Marine Science.
The aerial survey of the Reef, the first for this year, found severe bleaching in offshore reefs from north of Ingham to the northern extent of the survey near Cairns.
This year more bleaching is being observed in this central part of the Reef, which last year escaped widespread severe bleaching. The survey confirmed anecdotal reports from visitors and reef surveys of bleaching from marine park rangers and commercial operators, said David Wachenfeld, director of reef recovery at Marine Park Authority.
"Mass bleaching is occurring on the Great Barrier Reef for the second consecutive year. How this event unfolds will depend very much on local weather conditions over the next few weeks," Wachenfeld said. "Importantly, not all bleached coral will die. As we saw last year bleaching and mortality can be highly variable across the 344,000 square kilometres Marine Park - an area bigger than Italy," he said. The recurrence of widespread coral bleaching in back-to-back summers indicated there was not enough time between last year's extreme heat event for the corals to fully recover, said Neal Cantin from the Australian Institute of Marine Science (AIMS).
"We are seeing a decrease in the stress tolerance of these corals. This is the first time the Great Barrier Reef has not had a few years between bleaching events to recover," Cantin said. "Many coral species appear to be more susceptible to bleaching after more than 12 months of sustained above-average ocean temperatures," he added.
Marine Park Authority experts and scientists from the ARC Centre of Excellence for Coral Reef Studies will take to the sky again next week to resurvey 1150 reefs along the entire Great Barrier Reef.
This bleaching highlighted the importance of global action on climate change, Wachenfeld said. "It's vital the world acts to implement the Paris Agreement to reduce greenhouse gas emissions," he said.